Method of purifying exhaust gases of internal combustion engines



Sept. 29, 1964 P. R. ASHLEY 3,150,922

METHOD OF PURIFYING EXHAUST GASES OF INTERNAL COMBUSTION ENGINES Filed Jan. 16, 1961 INVENTOR. PAUL R.ASHLEY ATTORNEYS United States Patent 3,150,922 ME'IHGD OF PURIFYHNG EXHAIET GASES OF INTERNAL COMBUSTION ENGINES Paul R. Ashley, Livonia, Mich assignor to Calumet 8:

i-Iccla, inc, Alien Park, Mich, a corporation of Michigan Filed Jan. 16, 1951, Ser. No. 82,7? .3 cinms. c1. 23-2 This invention relates generally to catalytic smog prevention and refers more particularly to a method of and apparatus for reducing the hydrocarbon content in exhaust gases from an internal combustion engine.

Unburned exhaust products from the internal combustion engines of automobiles is believed to be a major factor in the smog problem which exists in certain parts of the country, and therefore automotive exhaust converters have been developed to remove unburned hydrocarbons and other objectionable components before they reach the atmosphere. In the operation of an automotive exhaust converter of the catalytic type, the exhaust gases are passed over the catalyst bed, heating the bed to a temperature at which the catalyst is effective to promote oxidation of the hydrocarbons. However, during the initial operation of the engine, the bed is below the minimum oxidizing temperature. Accordingly, during this initial period of engine operation, the unburned hydrocarbons pass into the atmosphere.

It has been discovered that during initial engine operation when the temperature of the bed is considerably below the minimum oxidizing temperature, the unburned hydrocarbons are adsorbed by the catalyst. The ad sorbed hydrocarbons are then released as the temperature of the bed rises. Unfortunately, however, at the time of release the catalyst bed is still below the minimum oxidizing temperature and hence the adsorbed hydrocarbons are released to the atmosphere.

One object of this invention is to provide a method of and apparatus for reducing the hydrocarbon content of exhaust gases from an internal combustion engine during the initial operation thereof.

Another object of the invention is to provide primary and secondary catalyst beds connected in series for the passage of exhaust gases across such beds in sequence, and means for rapidly heating the secondary bed to a catalytic oxidizing temperature while the primary bed remains at a temperature at which it adsorbs hydrocarbons, so that upon release of the adsorbed hydrocarbons by the primary bed, such released hydrocarbons will be oxidized by the secondary bed.

Other objects and features of the invention will become apparent as the following description proceeds, especially when taken in conjunction with the accompanying drawing, wherein:

FIGURE 1 is a semi-diagrammatic View of the apparatus embodying the invention.

FIGURE 2 is a semi-diagrammatic view illustrating a modification of the invention.

Referring now more particularly to the drawing, and especially to FIGURE 1 thereof, the reference numeral 19 designates the primary exhaust converter and the reference numeral 12 designates the secondary exhaust converter.

The primary exhaust converter comprises an elongated tubular casing 14 closed at either end by end walls 16 and 18. A screen 20 adjacent the end wall 16 extends across the casing in spaced relation to the end wall 16, and a screen 22 adjacent the end wall 18 extends across the casing in spaced relation to the latter end wall. The screens 20 and 22 are provided to confine a mass of catalytic material 24 in granular or pellet form. The screen apertures are somewhat smaller than the grains of cat- 3,150,922 Patented Sept. 29, 1964 alyst to confine them without interfering with the how of exhaust gases through the screens and through the catalytic bed.

The end member 16 is formed with an exhaust inlet 26 to the space between the end member and screen 20, and the other end member 18 is formed with an exhaust outlet 28 from the space between the end member and screen 22.

The secondary exhaust converter 12 is very similar to the primary exhaust converter. It comprises a tubular casing 39 which is considerably shorter than the casing 14. The ends of the casing are closed by the end walls 32 and 34. Screen 36 adjacent end wall 32 extends across the casing in spaced relation to such end wall, and a screen 38 adjacent to end wall 34 extends across the casing in spaced relation to end wall 34. The screens 36 and 38 are provided to confine therebetween the catalyst bed 49. The catalyst is in granular or pellet form, and the screen apertures are somewhat smaller than the grains of catalyst to contain them without interfering with the flow of exhaust gases.

The outlet 28 from converter 10 communicates with the space between end wall 32 and screen 36 of the sec ondary converter, and an exhaust outlet 42 is provided for the secondary converter, being in communication with the space between screen 33 and end wall 34 thereof.

No catalytic converter based on the oxidization of hy drocarbons can be effective unless there is su'iiicient oxygen introduced to complete the combustion of the unburned hydrocarbons. Any suitable air inspiration device may be used to provide secondary air. The secondary air may, for example, be introduced by devices such as a venturi, a flat-plate orifice, or a pump. The particular means for introducing secondary air forms no part of this invention and therefore it should be understood that any suitable means may be provided.

The catalyst forming the primary bed 2 and the secondary bed 4i? may be any suitable material designed to promote oxidization of the unburned hydrocarbons in the exhaust gases passing through the converter. For example, oxides of manganese and copper may be provided on a granular carrier of A1 0 Excellent results have been obtained with a ratio or": MnCu of 5:1 on an Al O carrier.

To complete the secondary converter 12, a heater 46 is provided for the secondary catalyst bed therein. In the present instance, the heater is shown in the form an electric coil surrounding the casing.

In operation, the exhaust gases enter the primary converter 19, pass through the primary catalyst bed 24, and then pass into the secondary converter 12 through the connection or conduit 28. The exhaust gases then pass hrough the secondary bed 49 in converter 12 and are discharged to the atmosphere through the outlet 42.

The catalyst beds 24 and 4d are heated by the exhaust gases passing therethrough. In the present instance, the minimum oxidizing temperature of the catalyst beds is about 300 F, and accordingly until the catalyst is heated to that temperature the hydrocarbons will pass through without being oxidized. it has been discovered that the catalyst material will adsorb hydrocarbons in a temperature range up to F, the adsorbed hydrocarbons being released by the catalyst in the temperature range of about 150 F. to about 300 F In order to oxidize the hydrocarbons adsorbed by the primary bed 24 during the initial engine operation, the relatively small, thin secondary bed 44 is rapidly heated at least to its minimum oxidizing temperature of about 300 F. by the coil 46. The coil 46 will be activated immediately upon starting the engine when the catalyst in both beds is relativeiy cool, and the secondary catalyst bed 4% will thus be rapidly heated to its minimum .same mass of catalytic material.

oxidizing temperature before the primary bed 24, heated solely by the exhaust gases, exceeds the maximum temperature at which it will adsorb hydrocarbons. Hence during the further temperature rise in the primary bed as engine operation continues, the adsorbed hydrocarbons will be released by the primary bed (this takes place in the temperature range between about 150 F. and about 300 F.) and will be oxidized upon passage through the secondary bed 40.

After a sufiicient period of engine operation to heat the primary bed by the exhaust gases at least to its minimum oxidizing temperature, the coil 4d may be deactivated and thereafter both beds Will promote oxidization of the hydrocarbons.

As an alternative, the secondary converter may be utilized only during the initial operation period, and when the coil 46 is de-activated the secondary converter may be bypassed. For this purpose a valve 50 may be provided in connection 23 for selectively providing communication between the converters and for diverting the discharge from convcrter directly to the atmosphere by way of bypass conduit 52. Accordingly, when the coil 46 is activated, the valve 50 will be conditioned to pass exhaust gases from converter 10 to converter 12, and when coil 45 is tie-activated the valve 50 will be conditioned to bypass converter 12 and divert the exhaust from converter 10 directly to the atmosphere by way of conduit 52.

FIGURE 2 shows a modification of the invention. The converter 10 there shown is exactly like the converter 10 in the first embodiment with the addition of a heating coil 46' surrounding the portion of the casing surrounding a thin section of the catalyst bed at the discharge end 55. The catalytic material may be the same as in the first embodiment and both catalyst beds are portions of the The secondary bed is that portion of the mass of catalytic material surrounded by the coil 46', and the remainder of the catalytic material constitutes the primary catalyst bed.

As in the first embodiment, the exhaust gases entering at inlet 26 pass through the converter 10 across the entire mass of catalytic material and are discharged through outlet 28. The coil 4-3 is activated immediately upon initial operation of the engine to bring the secondary catalyst bed surrounded by the coil rapidly to its catalytic oxidizing temperature while the primary bed, heated only by the exhaust gases, remains in a temperature range below 150 P. where it will adsorb hydrocarbons. Then upon further rise in the temperature of the primary catalytic bed to the range in which it releases the adsorbed hydrocarbons (in this instance, a range of about 150 F. to about 300 F.), the released hydrocarbons will be oxidized upon passing through the secondary bed. When the primary bed is heated at least to its minimum oxidizing temperature by the exhaust gases, the coil 46 may be tie-activated.

It will be understood that the catalytic material will eventually be heated by the exhaust gases to a temperature considerably above its minimum oxidizing temperature, and this is true in both embodiments. It will also be understood that the temperatures and temperature ranges recited herein are only approximate. In other words, the low temperature range during which hydrocarbons are adsorbed by the catalytic material is up to approximately 150 F., the intermediate range in which adsorbed hydrocarbons are released is approximately 150 F. to approximately 300 F., and it is at approximately 300 F. or above that the catalyst begins to promote oxidation. While the temperature ranges may vary somewhat, the important consideration is that initially the hydrocarbons are adsorbed, upon further temperature rise the adsorbed hydrocarbons are released, and at a somewhat higher temperature the catalyst begins to promote oxidation.

The drawings and the foregoing specification constitute a description of the improvement in catalytic smog prevention in such full, clear, concise and exact terms as to enable any person skilled in the art to practice the invention, the scope of which is indicated by the appended claims.

What I claim as my invention is:

1. Method for oxidizing hydrocarbons in exhaust gases from an internal combustion engine which comprises passing said exhaust gases mixed with secondary air sequentially through primary and secondary beds each containing the same catalyst consisting of aluminum oxide granules impregnated with manganese oxide and copper oxide, adsorbing the hydrocarbons from said exhaust gases in said primary catalyst bed during initial operation of the engine while the temperature of said primary bed is below oxidizing temperature for hydrocarbons, thereby temporarily restraining the hydrocarbons within the catalyst bed while permitting the remaining gases to pass through the secondary catalyst bed and to exit therefrom, applying auxiliary heat to said secondary catalyst bed to rapidly raise the catalyst therein to its oxidation temperature while the primary catalyst remains below said oxidation temperature, continuing the passage of said exhaust gases thereby gradually raising the temperature of the catalyst in said primary bed to a point where adsorbed hydrocarbons are released and are reintroduced into the flowing stream of exhaust gases, and passing the stream with its released hydrocarbons through the secondary catalyst bed, the temperature of which has been raised to the oxidizing point during the interval of adsorption and release, and continuing the passage of exhaust gases through the primary catalyst bed after the temperature thereof has reached the oxidation point.

2. Method for oxidizing hydrocarbons in exhaust gases from an internal combustion engine which comprises passing said exhaust gases mixed with secondary air sequentially through primary and secondary catalyst beds, each containing the same catalyst consisting of aluminum oxide granules impregnated with manganese oxide and copper oxide, adsorbing the hydrocarbons from said exhaust gases in said primary catalyst bed during initial operation of the engine while the temperature of said primary bed is below F., thereby temporarily restraining the hydrocarbons while permitting the remaining exhaust gases to continue through the secondary catalyst bed, releasing said adsorbed hydrocarbons from said primary catalyst bed as the temperature thereof increases from 150 F. to 300 F., thereby reintroducing said hydrocarbons into the flowing stream, rapidly heating said secondary catalyst bed to a temperature above 300 F. and oxidizing the hydrocarbons reintroduced into said stream as they pass through said secondary catalyst bed at a temperature above 300 F.

3. The method defined in claim 1 including diverting the exhaust gases from said primary catalyst bed directly to atmosphere when said bed has reached its required catalytic oxidizing temperature, thereby bypassing said secondary catalyst bed.

References Cited in the file of this patent UNITED STATES PATENTS 1,789,812 Frazier Jan. 20, 1931 2,071,119 Harger Feb. 16, 1937 2,942,932 Elliott June 28, 1960 FOREIGN PATENTS 411,377 Great Britain June 7, 1934 

1. METHOD FOR OXIDIZING HYDROCARBONS IN EXHAUST GASES FROM AN INTERNAL COMBUSTION ENGINE WHICH COMPRISES PASSING SAID EXHAUST GASES MIXED WITH SECONDARY AIR SEQUENTIALLY THROUGH PRIMARY AND SECONDARY BEDS EACH CONTAINING THE SAME CATALYST CONSISTING OF ALUMINUM OXIDE GRANULES IMPREGNATED WITH MANGANESE OXIDE AND COPPER OXIDE, ADSORBING THE HYDROCARBONS FROM SAID EXHAUST GASES IN SAID PRIMARY CATALYST BED DURING INITIAL OPERATION OF THE ENGINE WHILE THE TEMPERATURE OF SAID PRIMARY BED IS BELOW OXIDIZING TEMPERATURE FOR HYDROCARBONS, THEREBY TEMPORARILY RESTRAINING THE HYDROCARBONS WITHIN THE CATALYST BED WHILE PERMITTING THE REMAINING GASES TO PASS THROUGH THE SECONDARY CATALYST BED AND TO EXIT THEREFROM, APPLYING AUXILIARY HEAT TO SAID SECONDARY CATALYST BED TO RAPIDLY RAISE THE CATALYST THEREIN TO ITS OXIDATION TEMPERATURE WHILE THE PRIMARY CATALYST REMAINS BELOW SAID OXIDATION TEMPERATURE, CONTINUING THE PASSAGE OF SAID EXHAUST GASES THEREBY GRADUALLY RAISING THE TEMPERATURE OF THE CATALYST IN SAID PRIMARY BED TO A POINT WHERE ADSORBED HYDROCARBONS ARE RELEASED AND ARE REINTRODUCED INTO THE FLOWING STREAM OF EXHAUST GASES, AND PASSING THE STREAM WITH ITS RELEASED HYDROCARBONS THROUGH THE SECONDARY CATALYST BED, THE TEMPERATURE OF WHICH HAS BEEN RAISED TO THE OXIDIZING POINT DURING THE INTERVAL OF ADSORPTION AND RELEASE, AND CONTINUING THE PASSAGE OF EXHAUST GASES THROUGH THE PRIMARY CATALYST BED AFTER THE TEMPERATURE THEREOF HAS REACHED THE OXIDATION POINT. 